Selecting tomato seedlings

Selecting tomato seedlings in a cool climate

Selecting your tomato seedlings for planting – 8 October 2021
Hobart Show day is on the horizon and thus it is getting close to that time when tomato seedlings will be everywhere. Given we are really a marginal climate for tomatoes, it is important to look for a few things when picking your tomato seedlings to purchase and when to plant them.
1 – Pick tomato seedlings that have a purple colour at the base of the stem. This shows they are more hardened to our climate and have not lived in a hot controlled environment their whole life. When we have cooler summers like the past two and seems we are headed for a third, this can greatly improve them settling in.
2 – Don’t pick something that needs a stick to support it, It should be sturdy and fat stemmed.
3 – Look for lots of hairs on the stem
4 – Height is good. You can pull the bottom leaves off and plant deeper. The hairs on the stem become more roots, allowing a better root system to develop.
4 – A light green leaf is typical of mass produced seedlings in a controlled hot environment. Might be ok for planting out in mainland states, but not ideal in our marginal climate. (Note some varieties are lighter coloured so this can be confusing – point 1 to 3 are important)
5 – Variety matters. What is it you want, earlier ripening fruit or are you happy to get later toms? Cherry toms seem to do fine no matter what, it is just a matter of when they ripen. I recommend you plant at least 1 or 2 cooler tolerant varieties such as Gold Nugget, 42 days, Calmart, Glacier, Northern Delight, Kotlas, Siletz, Legend, Oregon Springs, Early Wonder/Annie to name some.
When to plant?
– I look for the minimum night temps as a start. When nights are consistently above 5 degree C I consider it. (Doesn’t happen every night where I am – Huon Valley, even in November thus protection is important
– Then I look at soil temps. Ideally 5 to 7 days where the soil temp is above 10 C (This can be challenging in Tasmania if our Spring is cool (as it is now).
– As we are marginal for tomato weather, all plantings when made should be protected to help get them through cold weather. At worst, use some stakes and the plastic tree guards. Ths also minimises wind impact (tomatoes dislike strong winds) and provides some form of warmth.
– Uncover if the days are warm (say sunny and over 18).
– Tomatoes thrive in temps between 18 and 28. We just need to get them through to December.
– Don’t fertilise at planting outside of manures and seasol. The temperature of the soil dictates how available the nutrients are to the plant. Wait till it warms up more to fertilise (mid Nov on as a general guide). Helps tell the plant to send its roots down and not hang around the surface.

Late Addition – Don’t cover your soil with mulch until the soils have warmed (sometimes not till x-mas) Cold soils will mean difficulty in the tomato drawing phosphorus from the soil resulting in a purplish colour under the leaves also – shouldn’t impact on the plant long term but covering the soil with mulch reduces the ability for the soil to heat up as the sun shines)

Lastly, I plant in 3 batches to mix up your planting dates. Last year my best tomatoes where planted early Nov, the year before early Dec and the year the Huon Valley was on fire it was Show Day. The weather tells us when to plant. Tomato seedlings sell fast, so get your seedlings and if needed pot up if you are not confident to plant.
Below is a list of earlier ripening tomatoes that have done well for me. They ripen mid Dec thru January depending on the variety and when planted. There are more but these are my picks for a good start.
Happy Growing
Selecting tomato seedlings
hardened off tomato seedlings
Note the hairy purple stems on the tomato seedlings

4 thoughts on “Selecting tomato seedlings in a cool climate”

  1. Fabulous post.
    I’ve been gardening a long time and still have so much to learn!
    Thanks for the heads up on looking for seedlings with purple in the stems.
    Great read.

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